We are requesting a continuation of the NICHD training grant in demography to the University of Pennsylvania. Six pre-doctoral positions are proposed. We are not requesting postdoctoral positions. The program we describe continues Penn's longstanding tradition of excellence in training in demography with support through a NICHD training grant. For the next grant period the program is enhanced by a better integration of advances in the understanding of the relationship between populations and health and in the methodological tools available for demographers and other social scientists to address the social, policy and public health challenges in the study of health and well-being of populations. The principal aim of the demography pre-doctoral program at the University of Pennsylvania is to train independent researchers who are prepared to play leading roles in social demography and population analysis, including the growth, structure, health and well-being of human populations. This goal is achieved through (i) intensive instruction in the methods, theoretical approaches, and empirical substance of demography and allied disciplines; and (ii) progressive incorporation of students into faculty research activities that will eventually branch into independent research. Central to the achievement of this goal is exposure of students to the demographer's modus operandi. Demography represents an approach to studying social phenomena that is-in important dimensions-distinct from other approaches in the social sciences, is relevant to social and health policies in the U.S. and abroad, and lies at the nexus of several disciplines.